44 Farmer .—Studies in Hepaticae : 
The archegonia occur in groups upon cushion-like pro- 
tuberances which arise immediately over a s vein,’ and 
almost always at a spot where it is just forking. Each 
archegonial group is enclosed in a circular involucre, whose 
free margin is toothed or fimbriated. 
There are seldom more than two or three archegonial 
groups formed on a frond, though I have seen as many as 
seven, and they are nearly always confined to the early 
branchings of the frond, and never, so far as I have observed, 
extend to the younger dichotomies. 
The archegonia in their development conform to the 
ordinary Hepatic type and need not therefore be dealt with 
here, though it may be mentioned that paraphyses, or 
mucilage-hairs, occur plentifully amongst them. Even before 
fertilization, a second sheath can be discerned within the 
involucre, but it is only after fertilization that this develops 
into the large colesula which is characteristic of the genus. 
This further growth however takes place immediately upon 
fertilization, and is the first visible sign of its having been 
effected. All division in it is limited to an annular zone 
situated at its base, just where it joins the frond, and nuclear 
division may be favourably studied in this region. 
But besides the effect of promoting the development of the 
colesula, fertilization also brings about a vast increase in the 
number and in the growth of cells occupying the base of the 
archegonial group, as well as in the fertilized archegonium 
itself. In this way the massive calyptra is formed, within the 
colesula, and it carries up the numerous barren archegonia on 
its growing surface. As at the base of the colesula, so also in 
this tissue, dividing nuclei can be conveniently studied. 
Nuclear Division in the Gametophyte . — The nuclei are very 
small, but they possess the great advantage of containing 
but few chromosomes, and in all cases when I have been 
able to estimate their numbers with certainty, there have 
always been present four chromosomes to each nucleus. 
Gentian violet and orange used as a double stain are very 
valuable in researches of this nature, the vividly stained 
